TABLE 5-1 Total Population for 2000


Difference from Census Count


Population (in millions)

No. (in millions)


Census count



DA base estimate




DA alternate estimate




A.C.E. estimate




NOTE: See text for discussion.

SOURCE: Robinson (2001a:Table 3).

underregistration of births, using the results of birth registration studies adjusted by interpolation and extrapolation (the latest study covered 1964–1968). Administrative data from the Immigration and Naturalization Service are used to estimate legal immigration, but they must be adjusted to fill in gaps for undocumented (illegal) immigration and emigration.

For the population aged 65 and over, estimates are constructed from Medicare enrollment statistics. The Medicare data are adjusted for those not enrolled, who were estimated to be 3.7 percent of people aged 65 and over in 2000.


The Census Bureau’s concerns about differences in the census, DA, and A.C.E. estimates of the total population are illustrated by the several different figures available for 2000 shown in Table 5-1. The census count is that reported for April 2000, including household and group quarters residents in the United States. The DA base estimate is that developed by demographic analysis as described above, which, at the time of the census, was the Census Bureau’s initial and best estimate of the “true” population to be used as a measure for evaluating overall census coverage. The DA alternate estimate is that developed by the Census Bureau in early 2001, which incorporated a higher allowance for net undocumented immigration than that included in the DA base estimate. The A.C.E. estimate is that developed by dual-systems estimation for the household population from the results of matching census enumerations and an independent postenumeration survey in a sample of blocks. For comparability with DA and the census count, the A.C.E. estimate is augmented by approximately 7.5 million people to cover residents of group quarters and people enumerated in other special operations not included in A.C.E. (e.g., the remote Alaska enumeration).2


There is also a postcensal estimate for 2000, which is the 1990 census count (not adjusted for net undercount) carried forward with data on births, deaths, and net immigration. We do not discuss the Census Bureau’s postcensal estimates program in this report.

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